It is acquired lens opacity occurring old age in the absence of a local or systemic disease. It affects both sexes equally.

The general features or senile cataract are:-

- Always bilateral (one eye precedes the other).

- Progressive to maturity and hypermaturity.

- Hard nucleus.

- No local or systemic disease can be found.

Types:-

It may be either:

- Subcapsular cataract.

- Cortical cataract.

- Nuclear cataract.

A. Subcapsular cataract

It may be either:

1. Anterior subcapsular cataract.

2. Posterior subcapsular cataract: It is very close to the nodal point, so that it causes marked drop of vision especially with miosis. So that patients will complain more during reading and bright light as sun light.

B. Senile cortical cataract

It is a slowly progressive process of opacification of anterior, posterior and equatorial cortex. It runs in 4 stages; incipient, immature, mature and the hypermature stages.

1. The incipient stage:-

There is early opacification of the cortex.

Diagnosis:-

Symptoms:

- Bilateral gradual painless drop of vision due to index hypermetropia and astigmatism.

- Fixed musca because the opacities throw a shadow on the retina.

- Halos around light because of the water vacuoles in the lens.

- Uniocular diplopia due to irregular refraction inside the lens.

- Vision is more affected in the night.

Signs:

The pacification process starts as vacuoles and clefts among the lens fibers. Later on the opacified lens fibers will appear as greyish white radial spoke like opacities within the cortex. They can be easily seen against red reflex.

2. THE IMMATURE STAGE (IMSC):-

There is dense, but incomplete opacification of the cortex. The patient will suffer from marked drop of vision. Examination against red reflex shows few clear areas. Examination by oblique illumination shows positive iris shadow.

Lens intumescence:-

It is a complication of the immature and mature stages where the lens absorbs a large amount of water. So that the lens will be swollen and full of water vacuoles. The patient will complain of rapid drop of vision. Pain may occur if the swollen lens blocks the pupil leading to acute secondary angle closure glaucoma (phaco-morphic glaucoma). This condition is treated by emergency lens extraction after medical control of IOP.

3. The mature senile cataract (MSC):-

There is total opacification of the lens cortex causing reduction of vision to HM or PL. The iris shadow is negative. Red reflex is completely absent.

4. The hypermature senile cataract (HMSC):-

The forms of hypermaturity are:

a. Calcification of the capsule:-

This can occur either alone or with any of the following 2 forms of hypermaturity.

b. The shrunken form:-

It occurs due to gradual breakdown of lens proteins. They will be absorbed gradually through the lens capsule leading to shrinkage of the lens. Clinically the following signs are seen:-

- Deep anterior chamber.

- The lens is away from the iris leading to positive iris shadow.

- Tremulous iris.

- The lens capsule is wrinkled and may show calcifications.

.

c. The Morgagnian form:-

The lens cortex is liquefied and retained as a milky material inside the stretched capsule and the nucleus will sink down within the lens

Complications of HMSC:-

The HMSC is liable for the following complications:

1. Phacolytic glaucoma:-

- It occurs due to leakage of denatured lens proteins through the rarefied lens capsule. The lens matter will engulfed by macrophages that will obstruct the trabecular pores leading to glaucoma.

- It is an acute, congestive secondary open angle glaucoma.

- The anterior chamber is deep and contains a white matter which is nothing but macrophages laden with lens matter.

- It is treated by emergency ECCE + IOL after medical control of IOP.

2. The zonule becomes progressively weaker and may rupture due to mild trauma leading to:-

There is exaggeration of the physiological process of dehyration of the lens nucleus. This will lead to increasing the refractive index of the nucleus (causing myopic shift) followed by opacification of the nucleus. Pigmentation of the nucleus occurs due to abnormal metabolism of the tyrosine amino acid (tyrosine is the source of melanin). So that the nucleus will become grey, yellow, brown then black (cataracta nigra = black nuclear cataract).

Symptoms:

- Early, there is progressive myopia, so that the patient can read without presbyopic correction (the second sight), but he will complain of indistinct far vision .

- Later on, the patient will complain of bilateral gradual painless drop of vision especially in the light (day blindness) because of the central lens opacity.

Signs:

a. By oblique diffuse illumination and slit lamp examination the nuclear opacity is seen with its colour.

b. The red reflex is dim in the canter and clear in the periphery.

MANGEMENT OF SENILE CATARACT

Cataract extraction is done only after evaluation of the retinal condition, then optical correction of aphakia has to be done.

I. Evaluation of the case:-

This is very important to avoid complications and toknow if surgery is hopeful or not.

A. Preoperative examination of the eye:-

- The ocular surface (eyelids, conjunctiva and cornea) should be free from infections and other diseases.

- Examination of the anterior chamber, iris and pupil is done to exclude diseases that will affect the outcome of surgery as uveitis.

- Measure the IOP to exclude glaucoma.

B. Evaluation of retina and optic nerve functions:-

1. Subjective evaluation:-

a. Visual acuity should be matching with the density of cataract. It should be at least HM or PL with very dense cataract. No PL means damage of the retina or optic nerve (hopeless surgery).

b. Normal colour perception (assessment of macular function).

c. Light projection test: It is done in cases of mature cataract for assessment of the visual field. The patient is asked to fix his eye to his own finger in a dark room. A focused low intensity light is presented to his eye from 50 cm distance from various directions. The patient should identify the correct direction of light even with a very dense cataract. Bad light projection means unhealthy retina or optic nerve and poor surgical prognosis.

2. Objective evaluation:-

a Fundus examination if the cataract is not dense.

b. Ultrasonography: The A-scan is used to measure the antero-posterior diameter of the eye for IOL power calculation. The B-scan gives two dimensional image of the eye to show diseases as retinal detachment or vitreous hemorrhage.

c. The pupil should react normally to light.

d. Electrophysiolgical investigations:

* Electroretinogram (ERG) is used to evaluate the outer retinal layers.

* Visual evoked potential (VEP) is used to evaluate the conduction through the optic nerve.

II. Surgical techniques:-

A. Indications and timing of operation:-

1. To improve vision:-

- In IMSC and NC we interfere when cataract is dense enough to interfere with patient's activities.

- In MSC and HMSC we interfere without delay for fear of complications.

- We start by the more advanced eye because it is more liable for complications.

- If both eyes have mature cataract we wait few days between both eyes for fear of endophthalmitis.

2. Peripheral iridectomy should be done to avoid secondary ACG due to pupillary block by the vitreous face.

3. Removal of the lens within its intact capsule, usually by cryo.

* Disadvantages:-

- No posterior chamber IOL implantation.

- High incidence of retinal detachment and vitreous loss.

- Very large incision (nearly half of the limbus) leading to high astigmatism.

* Indications:

- Hard cataract with subluxation or dislocation.

* Contraindications:-

- When ECCE can be done.

- In young age because the zonule and capsulohyaloid ligament are very strong.

III. Optical correction of aphakia:-

1. Glasses according to postoperative retinoscopy (average power is +10 D. for far vision and +13 D. for near vision). The disadvantages of aphakic glasses are:

a. Marked magnification of image about 30%. So that they are contraindicated in cases of unilateral aphakia because they lead to intolerable aniseikonia and binocular diplopia.

b. Field contraction, prismatic effect and image distortion.

c. Bad cosmetic appearance.

2. Contact lenses: the power is measured by retinoscopy (+13 for far vision in average. For near vision + 3 D. glasses are added). They cause image magnification about 10% which can be tolerated in unilateral aphakia. Disadvantages of contact lenses are:

- Need special care.

- Corneal ulcers.

- Giant papillary conjunctivitis.

3. IOL: The power is calculated preoperatively by a special equation using the corneal refractive power (measured by keratometer) and axial length of the eye (measured by ultrasonography A-scan). The average powers are about +20D for PC-IOL. or +18 for AC-IOL.. For near vision we add +3 glasses).

NB. AC-IOL is supported in the angle, so that it may be complicated by uveitis, glaucoma or hyphema (UGH syndrome).

NB. Complications of cataract surgery:

I. Intraoperative complications:

1. Retrobulbar hematoma due to local anaesthesia. We have to postpone the operation otherwise vitreous loss and other operative complications will occur.

2. Intraocular hemorrhage that may be severe and expulsive.

3. Rupture of the posterior capsule during ECCE.

4. Vitreous loss especially in ICCE. The prolapsed vitreous should be excised (never aspirated) from the wound and anterior chamber.